1. Field of the Disclosure
The present disclosure relates to a controller and a method for detecting a signal activity on a bus.
2. Description of Related Art
In systems where several individual masters can be connected to one slave, as e.g. single cable satellite antenna systems, more than one master can start to transmit data to the slave at the same time. This may lead to data collision and thereby to data loss. To guarantee a satisfactory operation of all transmitting units it is necessary to provide means to detect and avoid data collision.
In single cable satellite antenna systems, several receivers are connected to a single cable interface (SCIF). Usually up to 8 individual receivers can be connected to the SCIF. Each of them can be tuned to a different frequency. A common standard is to use the “Digital Satellite Equipment Control Bus” (DiSEqC) for the communication between the receivers and the SCIF.
According to the Single Cable standard (EN 50494:2007—Satellite signal distribution over a single coaxial cable in single dwelling installations) a supply voltage between 12.5 and 14 V is applied by each receiver or satellite receiver to the bus that connects the SCIF with the receivers as long as no control data are transmitted from the receivers to the SCIF. For each receiver the supply voltage is raised before transmitting data to a transmission voltage between 17 V and 19 V. The DiSEqC command starts after a time interval of 4 to 22 ms. After transmitting data the voltage is lowered to the supply voltage within 2 to 60 ms.
Detection and avoidance of data collision is not a part of DiSEqC standard commands. Especially for a blind channel search in a single cable environment a DiSEqC standard command collision should be detected, to avoid wrong transponder search results. During large parts of such a scan normally no transport stream can be received as the frequency positions of potential transponders, which include these transport streams, are still unknown. During the remaining parts such a transport stream might be received, but still no reference exists to decide whether the received transport stream corresponds to the frequency selected by the DiSEqC command or not.
There is a need for providing a method and a controller that are able to prevent collisions and improve collision detection without the use of transport stream information.